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OFDM 기반의 WLAN을 지원하는 디지털 IF단 설계
박찬훈,신동우,최연경,양훈기,양성현,박종철,Park, Chan-Hoon,Shin, Dong-Woo,Choi, Youn-Kyoung,Yang, Hoon-Gee,Yang, Sung-Hyun,Park, Jong-Chul 한국정보통신학회 2011 한국정보통신학회논문지 Vol.15 No.8
본 논문에서는 OFDM 기반의 WLAN을 지원하는 Digital IF 단을 설계하고 시뮬레이션을 통해서 시스템 성능을 조사한다. 이를 위해서 ADC 샘플률, NCO 주파수 및 데시메이션률 결정과정을 보이고 주워진 데시메이션률을 얻기 위한 CIC필터 및 MHBF 설계과정을 제시한다. 데시메이션 과정에서 발생되는 진폭왜곡 보상을 위해 시스템 복잡도를 최소화하면서 요구성능을 만족시키는 ISOP 필터 및 FIR 필터를 설계하는 과정을 제시한다. 최종적으로 설계된 DDC 블록에 대해서 BER 관점으로 성능을 조사한 후 이론적인 변복조 시스템과의 성능 차이를 보인다. In this paper, we propose the design procedure of a digital IF system for the OFDM based WLAN system and examine its performances. Along with the decision procedure of ADC sample rate, NCO frequency and the required decimation ratio, we show the decimation ratio is accomplished through the use of a CIC filter and a MHBF. We also show that the amplitude distortion occurred in the decimation filters can effectively be compensated by a ISOP filter and an additional FIR filter, which leads to the reduction of the overall hardware complexity. Finally, we examine the BER performance of the proposed system and compare it with a theoretical one that excludes filter non-linearities.
최윤주,최웅철,양석우,최연경.Youn Joo Choi. M.D.. Woong Chul Choi. M.D.. Suk Woo Yang. M.D.. Yeun Kyoung Choi. M.D. 대한안과학회 2005 대한안과학회지 Vol.46 No.1
Purpose: We report a case of orbital abscess secondary to acute dacryocystitis in which the patient had been cared for chronic dacryocystitis. Methods: A 59-year-old woman presented to our clinic with a history of chronic sinusitis from childhood and right chronic dacryocystitis treated for 6 years. She had sufferred from influenza 2 weeks previously and complained of painful lid swelling, limitation of ocular movement, exophthalmos, chemosis, and decreased vision of the right eye for 2 weeks. An orbital CT scan was taken and bacterial culture and sensitivity tests were done from the discharge. Results: CT scan showed inflammation and abscess formation around the right nasolacrimal duct orifice which was swollen and widened. Some of the inflammation tissues extended into the retrobulbar portion. Streptococcus pyogenous was cultured. Lid swelling, pain, exophthalmos, and visual acuity improved after external dacryocystorhinostomy, and surgical drainage. Conclusions: We should be careful in a case of acute dacryocystitis underlying chronic dacryocystitis as it easily causes complications, and in such a case early surgical management as well as antibiotics therapy is more effective.